ABSTRACT
This chapter states simple trigonometric identities, proves simple identities and solves equations requiring trigonometric identities. In software engineering, working, say, on the next big blockbuster film, trigonometric identities are needed for computer graphics; an RF engineer working on the next-generation mobile phone will also need trigonometric identities. In addition, identities are needed in electrical engineering when dealing with a.c. power, and wave addition/subtraction and the solutions of trigonometric equations often require knowledge of trigonometric identities. With trigonometric identities it is necessary to start with the left-hand side and attempt to make it equal to the right-hand side or vice-versa. It is often useful to change all of the trigonometric ratios into sines and cosines where possible.
